The invention concerns a process for the treatment of a filament cable in a device into which it is introduced, crimped, trated with a gas and withdrawn.
Various kinds of filament cables must undergo drying, relaxing or thermosetting stages, in particular after washing, stretching or softening, in order to obtain a desired moisture content and particular values for properties such as expansion, strength or affinity for dyes. Moreover filament cables of this kind are usually crimped in order to prevent the filament cables from falling apart into individual threads and in order to attain, for the cut filaments, sufficient adhesion for the subsequent spinning process. The drying, relaxing and thermosetting stages are usually carried out by the treatment of the cable with a gas, especially with steam or heated air. Particular periods of direct contact must be adhered to for these steaming and drying processes.
In conventional subsequent treatment processes with low product rates of up to 150 m per minute and large band weights of, for example, 100 ktex, the required times of direct contact are attained with the aid of perforated drum dryers, which contain a row of perforated drums, for example, 20 to 30 drums with a diameter of 140 cm. The drying is carried out with heated air whereby air speeds of 3 to 5 m per second must be applied in order for adequate drying to be achieved. The energy requirement which is necessary for this process is very considerable. Since a residual solvent or a residual monomer is also always expelled from the filament cable during steaming and drying it is necessary for the drying devices to be closed to the surroundings which, however, is only partially successful in the case of a perforated drum dryer. The crimping is usually carried out after drying.
In continuous subsequent treatment processes which follow dry spinning processes, for example, with wind-off speeds of between 50 and 400 m per minute, speeds of, for example, 100 to 2000 m per minute arise, brought about by stretching. With these speeds and stretched product guiding such as is necessary on perforated drum dryers, the periods of direct contact required for drying cannot be achieved with realistic device sizes. For this purpose, what are termed "travelling filter dryers" are well-known on which the productd is piled up in a meandering shape with little tension and transported through the treatment areas in this way. The low tension, mostly tensionless piling-up on the travelling filter has the disadvantage that initially piled-up product layers of the folded cable drop down and are always covered by product layers which have been piled-up later, with the result that when the cable is unwound from the travelling filter a large proportion of the cable must be pulled out from underneath the rest of the cable. This can cause tangled layers, knotting, and thus problems in the progress of the process. In order to eliminate this disadvantage, the cable must be piled up on what are termed "turning drums" before introduction into the steaming or drying device and these drums ensure that when the cable is piled up onto the travelling filter, the product layers which are piled up first come to rest from above and can be unwound without any problems.
One disadvantage involved in this complicated technique is the fact that it is difficult to seal the device on the product inlet side with the result that large quantities of air are unnecessarily carried into the device and are included in the heating up, or harmful emissions emerge from the leaks. Furthermore, because of the turning drum the cable cools down and thus energy is lost.